Big head mode:
Highlight a fighter on the character selection screen. Then, hold L2 and press Circle. 

Small fighters: 
Highlight a fighter on the character selection screen. Then, hold R2 and press Circle.

Kid Mode: 
Hold down R2 when selecting character

Big Stage: 
Defeat 10 people in survival mode

Slant Move: 
Finish time attack in under 10 minutes

Large Arms: 
Finish Arcade at level 4 or higher with anybody without using continues

Small Stage: 
Finish Arcade at level 4 or higher with Greg (Ape)

No Walls: 
Finish Arcade at level 4 or higher with Mitsuko (Boar)

Invisible Walls: 
Finish Arcade at level 4 or higher with Fox (Fox)

Regenerating Life: 
Finish Arcade at level 4 or higher with Bakuryu (Mole)

No Gauges: 
Finish Arcade at level 4 or higher with Yugo (Wolf)

No Lighting: 
Finish Arcade at level 4 or higher with Long (Tiger)

No Blocking: 
Finish Arcade at level 4 or higher with Gado (Lion)

Position Camera: 
Finish Arcade at level 4 or higher with Alice (Bunny)

Alternate Alice:
Finish Arcade at level 6 or higher with Alice (Bunny). Hold down start when you select her.

After Image Mode:
Finish Arcade at level 4 or higher with everyone.

To Get Uriko:
Beat the game with Mitsuko 5 times in a row wihout losing more than twice.

Super deformed mode:
Go to your character you wish to do this on and hold R2 and press square.